CVE-2026-23270

In the Linux kernel, the following vulnerability has been resolved:

net/sched: Only allow act_ct to bind to clsact/ingress qdiscs and shared blocks

As Paolo said earlier [1]:

"Since the blamed commit below, classify can return TCACTCONSUMED while the current skb being held by the defragmentation engine. As reported by GangMin Kim, if such packet is that may cause a UaF when the defrag engine later on tries to tuch again such packet."

actct was never meant to be used in the egress path, however some users are attaching it to egress today [2]. Attempting to reach a middle ground, we noticed that, while most qdiscs are not handling TCACTCONSUMED, clsact/ingress qdiscs are. With that in mind, we address the issue by only allowing actct to bind to clsact/ingress qdiscs and shared blocks. That way it's still possible to attach act_ct to egress (albeit only with clsact).

[1] https://lore.kernel.org/netdev/674b8cbfc385c6f37fb29a1de08d8fe5c2b0fbee.1771321118.git.pabeni@redhat.com/ [2] https://lore.kernel.org/netdev/cc6bfb4a-4a2b-42d8-b9ce-7ef6644fb22b@ovn.org/